Slotted antenna system



Nov. 24, 1953 G. H. BROWN 2,560,674

SLOTTEID ANTENNA SYSTEM Filed Oct. 14, 1948 2 Sheets-Sheet l \NVENTOR r0mam/z 60 GEORGE BROWN AT ORNEY Nov. 24, 1953 G. H. BROWN 2,660 674SLOTTED ANTENNA SYSTEM Filed Oct. 14, 1948 2 Sheets-She'=t 2 OIPLEXER um24 52 $54 r0 V/SZ/AL/ 2 T0 All/R41 TRAMS'. TIM/K5- U/V/T 70 40 041 r0wsu/u mus. TRANS.

INJENTCER GEORGE H. BROWN ATTORN EY Patented Nov. 24, 1953 SLOTTEDANTENNA SYSTEM George H. Brown, Princeton, N. J., assignor to RadioCorporation of America, a corporation of Delaware Application October14, 1948, Serial No. 54,462

26 Claims. 1

The invention relates to high frequency antenna systems and particularlypertains to high frequency antennas providing uniform radiation patternsin the horizontal plane.

Several ultra-high frequency antenna systems for broadcast and otherservices requiring uniform radiation in the horizontal plane are knownto the art. The turnstile antenna, having four horizontal radiatingelements emanating from a vertical supporting member in a mannersuggestive of its name, has proved to be particularly useful intelevision broadcasting because its construction is simple, highvertical directivity is easily attained by stacking a number ofradiating-element layers, and the required phase-quadrature relationsrender it feasible to employ simple networks to apply both visual andaural excitation. The terms visual and aural excitation as herein usedwill be construed to mean radio Waves modulated by signals proportionalto picture tones and sound variations desired to be transmitted forentertainment or other purposes. The pylon antenna has provedparticularly advantageous for broadcast service especially in frequencymodulation applications. The Pylon Antenna described in copending U. S.patent application Serial No. 593,152, filed May 11, 1945, by WoodrowDarling, now U. S. Patent 2,513,007, issued June 27, 1950, basicallycomprising a vertical cylinder with a slot cut along one side and havinga feed line connected across the slot at the center thereof, is alsosimple in construction and particularly adaptable for stacking a numberof such elements in the vertical directions to improve the verticaldirectivity while maintaining a uniform horizontal radiation pattern.There is a third high frequency broadcasting antenna described in copending U. S. patent application Serial No.

718,791 filed December 2'7, 1946, by John E. Pauch,

now U. S. Patent 2,568,560, issued September 18, 1951, sometimes knownas the prismatic antenna, comprising a plurality of vertical radiatorelements arranged in the horizontal plane to form an interruptedgeometrical pattern as a prism interrupted at the corners thereof, theinterruptions of which when viewed in the vertical direction can beconsidered as open-ended slots, which slots are fed at the center muchin the same manner as that of the pylon antenna to produce a uniformhorizontal radiation pattern. This latter type of antenna is fairlysimple in construction and may be varied in height to provide a desiredvertical directivity while maintaining uniform radiation in thehorizontal direction.

The above mentioned antennas have proved entirely unsatisfactory whenthe frequency of the carrier wave is of the order of 500 megacycles andhigher. The radiators conventionally employed with the turnstileantennas then become exceedingly difficult to construct and also thesupporting member approaches an appreciable fraction of the operatingWavelength. The pylon antenna has the serious disadvantage that in orderto produce a relatively uniform radiation pattern the horizontalcross-section of the antenna must be small, giving rise to a largeinductive reactance component which tends to make the interior act as awave guide, thus establishing a cut-off which is highly undesirable andnecessitates complex measures to neutralize the same. Although fairlysimple in construction, the barrel-stave antenna is inherentlymechanically weak, requiring complex insulating and spacing provisions.

These and other, more complex, antenna systems have been also employedheretofore in radio navigation applications where the inherentdisadvantages mentioned in regard to program broadcast services are evenmore apparent and, in addition, any non-circularity of the radiationpatterns which for program broadcast service may be permitted to acertain extent even though undesirable, simply cannot be tolerated forthe latter purposes. In order to eliminate the error introduced bynon-circularity of the radiation pattern, complex systems have beendevised and employed at great expense in efliciency and economy.

Furthermore, the prior art radio navigation systems have usuallyrequired complex antenna systems because of the manner in which waveenergy is desired to be radiated. For example, the omni-directionalrange heretofore usually employed utilizes an antenna system havingfive, closely spaced, individual, loop antennas interconnected and fedwith radio frequency energy in the desired manner. Obviously, such acomplex arrangement has been employed as a necessity rather than adesirability since the close spacing required of the individualradiators results in an undesirably low radiation resistance and thecoupling between radiators results in serious unbalance. Furthermore,the horizontally polarized omni-range exhibits a large 00- tantal errordue to the inability to keep the phase displacement factor small withloop antennas; where d is the spac ing between antennas and is thewavelength, both in meters.

The above described disadvantages are obviated in an ultra highfrequency antenna system according to the invention wherein a simpleconductive tubular member capable of being integrally joined to a rigidmechanical supporting element is provided with a plurality of slotswhich are excited with high frequency energy in a simple and eificientmanner effecting capacitive .reactance in the interior of the antennaand providing radio frequency conditions along the conductive memberwhereby the use of simplified and compact feeder assemblies arepracticable even for installations calling for a relatively complexmethod of excitation.

Accordingly, one of the objects of the invention is found in the designof an efiicient ultrahigh frequency transmitting antenna.

Another object of the invention is to provide an ultra-nigh frequencytransmitting antenna capable of uniform radiation in all directions in ahorizontal plane about the antenna.

A further object of the invention is to provide an ultra-high frequencytransmitting antenna having a circular horizontal radiation patterntogether with compression of the radiation in the vertical direction.

Still another object of the invention is to provide an antenna systememploying a tubular metal structure and avoiding the cut-off effect ofthe normal wave guide.

A. still further object of the invention is to provide a multiple-slotantenna capable of radiating energy in response to excitation from aplurality of R. F. sources.

Yet another object of the invention is to provide an efficient ultrahigh frequency modulation broadcast antenna.

Yet a further object of the invention is to provide an antenna systemfor omni-directional ranges having low octantal error and a singleradiating element providing simplified construction and installation.

It is still another and further object of the invention to provide apractical antenna design which permits a plurality of antenna sectionsof novel design to be supported by a single conductive supportingmember.

These and other objects of the invention will appear as thespecification progresses.

The invention will be described in detail with reference to theaccompanying drawing forming a part of the specification and in which:

Figure 1 is a diagram illustrating the mode of operation of an antennasystem known to the art;

Figure 2 is an illustration of the radiating elements of an antennasystem according to the invention;

Figure 3 is an illustration, partly in crosssection and partly inperspective, of the novel method of feeding the radiating elements shownin Figure 2;

Figure 4 is a further illustration of the method of feeding theradiating elements of the type shown in Figure 2;

Figures 5 and 6 are illustrations of feeder harnesses for applying ultrahigh frequency energy according to the invention to the antennastructure shown. in Figure 2; and

Figures '7 and 8 are illustrations of the method of feeding alternateembodiments of the invention.

In order that the antenna system according to the invention be morereadily understandable, reference is first made to the mode of operationof a known antenna system from a discussion of which novel features ofthe invention will become apparent as the specification progresses.Referring to Fig. 1, there is shown a cross section of a knownmultiple-slot antenna taken at the center of the slots at which :pointradiatingelements H, I2 and I3 are excited at the edges thereof in theconventional manner by means including afeeder assembly l4 comprising acoaxial feed line I6 connected in parallel to distributor feeds I1, 18and IS. The inner conductors of feeders ll, l8 and I9 are connected tocorresponding edges of radiators H, l2 and I3 respectively while theouter conductors are connected to the adjacent radiator immediatelyacross the slots or gaps formed between the radiators as shown inFig. 1. Applied in this manner, the instantaneous currents flowing inthe radiators proceed in the same direction around the assembly asindicated by the solid arrows to -produce a radiant energy fieldradiating from the assembly with uniform intensity. In this conventionalantenna assembly it should be noted that the same instantaneouspotential exists across all of the slots and that corresponding edges ofthe slots exhibit the same instantaneous potential.

Referring to Fig. 2 there is shown an embodiment of an antenna accordingto the invention which comprises a supporting member 20 and fourradiating element members 2I-24, each of which is exactly similar to theothers. For pur- 'slots cut into the uppermost end of the structure atthe proper loci. It is of course to be understood that a single elementor any number of them may be used with the results dependin upon thetype of radiation desired. For example, it is anticipated that for FMbroadcast services a four-element antenna will be found most desirablefor general use, while in radio navigation applications, it will in allprobability be found that but one element will be suflicient for mostinstallations and this is particularly anticipated for installationsinvolving mobile or transportable equipment.

Particular reference will be made to only one of the radiating elementsas an illustrative example in explanation of the novel features of theinvention. Referring still to Fig. 2, it will be seen that a radiatingelement is constituted by a metallic cylinder 24 having fourlongitudinal slots 3l-34 cut into the walls thereof. In the preferredembodiments of the invention slots 31-34 are equidistantly spaced aroundthe periphery of cylinder 24; however, it is to be understood that it iswithin the scope of the invention to employ more or fewer slots, equallyor unequally spaced in accordance with the intent of the designer andthe problems at hand. For convenience slots 3|34 are referred tohereinafter as north, east, south and west slots, which designations arereadily associated with the corresponding cardinal points of the compassand tend to present a clearer understanding of the adaptation of thesubject antenna to types of problems for which it was principallydesigned.

Further in the interest of clarity and convenience the longitudinaledges of each pair of slots which lie diametrically opposite each otheror which appear in the same relative position in a traverse about theperiphery in a single direction are termed the corresponding edges, andthe edges which are immediately opposite each other are termed theopposing edges as against the apposing edges of the same slot. Forexample, edges 48 and 41 of the section shown in Fig. 3 are apposingedges, as are edges 48 and 49. Edges 41 and 49 which are diametricallyopposite each other are corresponding edges, while opposing edges 41 and48 are immediately opposite each other. With respect to a given edge 46,the edge 47 of the same slot is the apposite edge; the immediatelyopposing edge 49 is the opposite edge; and the diametrically oppositeedge 48 is the corresponding edge.

Referring to Fig. 3 there is shown a cross section of element 24 of Fig.2 taken on line 3-3. Radio frequency energy is applied to theradiatingelements of the novel antenna in a manner according to theinvention as shown in Fig. 3 wherein there is provided a coaxialtransmission line 37 which is bifurcated to form lines 38 and 39 ofequal length supplying energy in the same phase relationship to the eastand west slots at the centers thereof. The center conductors of lines 38and 39 are connected to opposite edges 42 and 45 of the east and westslots and the outer conductors are connected to opposite edges 43 and 44of the east and west slots respectively. It will be seen from aninspection of Fig. 3 that the instantaneous currents flowing around theperiphery of radiator element 24 from the points just mentioned flow inopposing directions as shown by the solid arrows, that is exactly theopposite of the known antenna shown for comparison in Fig. 1. By meansof these connections magnetic fields will be set up in the east and westslots but no field will be set up in the north and south slots. This hasbeen proven by actual test in which it has been found that the radiationin the horizontal plane may be accurately expressed by the Quantity Cos0, where 0 is the angle measured with the east direction taken as 0equal to 0. This last expression has been found extremely accurate forany diameter of radiator element lying between and A of the operatingwavelength.

For the sizes of structure usually used, the pylon prismatic antennas.previously mentioned exhibit an inductive internal reactance whichtends to make the interior of the structure function as a wave guide andestablish a cut-off frequency below which the antenna will not function.This effect is highly disadvantageous and is a factor tending to limitthe use of the latter antennas. However, because of the novel manner inwhich the antenna of the invention is fed, the internal reactance ismade capacitive in nature. Thus, by means of this heretofore unknownfeature an antenna can be produced which not only avoids one of themajor objections to the antennas of the prior art but also permits theradiation of highly desirable complex waves as will now be shown.

It should be noted. that when applying radio frequency energy toradiator element l l as shown in Fig. 3 both apposite edges 46, 41, ofthe south slot are at equal potential and apposite edges 48 and 49 ofthe north slot are likewise at equal potential though diifering fromthat of the former. Recognizing this fact, it can be seen that a similarR. F. feed system can be connected to the south and north slots with nointeraction occurring between the application of R. F. energy to theeast and west slots and the north and south slots. This is shown betterin Fig. 4 wherein the element 24 has been figuratively unrolled topresent a clear and readily understandable diagram of the method of feedin which the east and west slots are fed by means of the harnessassembly previously described with reference to Fig. 3 and the north andsouth slots are fed by a transmission line assembly exactly similar tothat previously described but so connected that interaction of energybetween the two sets of slots is avoided.

Referring again to Fig. 2 there is shown a practical embodiment of anantenna according to the invention useful in transmission of televisionsignals wherein four radiator elements 2l-24 are fastened together bymeans of flanges 26, 27 and 28 to form a unitary structure which issupported on a suitable column 2|] by means of flange 25. As previouslystated, it is not at all necessary to employ separate sections, however,and it is contemplated in practice to construct such an antenna andsupporting member in the form of a single tubular member having thenecessary slots cut into it in the desired loci. The slots are spaced awavelength apart from center to center in the vertical direction, and ithas been found in practice that slots 3!, 32, 33 and. 34 may be anywhereone half wavelength to a full wavelength long. However, it has beenfound that for the usual coaxial transmission line slot lengths lyingbetween 0.75 and 1.0 wavelength are better and preferably a slot lengthof 0.85 wavelength is employed. With a slot length of 0.85 wavelength animpedance of approximately 25 ohms is obtained in either direction fromthe center of the slot at which the energy is applied, which impedancehas been found very convenient to use. The slots are energized bytransmission lines connected on the inside of the radiator elements bymeans of coaxial transmission lines as shown in the remaining figures ofthe drawing. For example, the system as previously described inreference to Fig. 4 can be employed for television broadcasting byutilizing a qu ater-wave phasing loop 5| inserted, in line 37, but whichmay with equal effect be inserted in either one of the transmissionlines 37 or 51 which are in turn connected to a well known diplexer 52(such as is disclosed in copending U. S. application, Robert WayneMasters, Serial Number 714,620, filed December 6, 1946, now U. S. Patent2,570,579, issued October 9, 1951), to which transmission lines 53 and54 are connected to an aural transmitter and a visual transmitterrespectively. The two sets of slots are fed in phase quadrature, thusproducing the equivalent radiation of that produced by the turnstileantenna. Referring to the previously established reference angle, thenorth and south slots radiate according to the law sin 0. and if thenorth and south slots have R. F. energy applied to them in phasequadrature to that applied to the east and west slots, the resultantfield will be cos 6+ sin. 0, which will be immediately recognized as theexpression of a perfect circle.

The arrangement of Fig. can be extended to any number of elementsstacked in the vertical direction.

Referring to Fig. 5 there is shown a portion of an R. F. feed assemblyarranged in the interior of a structure according to Fig. 2, the stackof assume north :slots :only being shown for convenience, it ibein'gunderstood that 'the remaining slots are fed 'in :similar fashion. Aconcentric transmission line fill is bifurcated into transmission lines6! and 562 of equal length to apply R. F. energy in thesame phase tonorth andsouth slots. Trans- ;mission line [it is again bifurcated toform .secondary transmission lines 63 and $4 of equal lengthdividing-again into four additional transmission lines 85. $6, 5? and 63respectively, each heing'three-quarter wavelengths long and 50 ohmsimpedance. I he outer conductors of transmission lines .65 and-filiareconnected tocorrespondfing edges 99, 89 of the lowermost slots of thenorth stack while the inner conductors are connected to correspondingedges -98 and 88 respectively. The corresponding edges 38 and 180i thetwo uppermost slotsare connected to the center :conductors oftransmission lines 68 and 51 while the corresponding'edges 49 and :9 areconnected .to theeuter conductors thereof. In this manner correspondingedges 4%. i8, 852 and 93 are con- :nected in the same phase and inopposition to that of the respective opposite edges 49, 19,89 and 99.

Asimpler feeder assembly-providing equivalent results of that describedis shown in Fig. 6 whereinedges ail-and is of the two uppermost slotsare connected together by the outer conductor of a imultiple-ofwavelengths of transmission line 12, one end of whoseconductor isconnected to edge 49 of the uppermostslot. Similarly corresponding edges88 and 98 of .the lowermost slots are connected together by the outerconductor of a .multiple of wavelengths of transmission line H, one endof whose innerconductor is connected toedge of -95 of the lowermostslot. A solid dielectric transmission line of one and one-halfelectrical wavelengths and having a physical length of approximately onewavelength is conveniently employed in practice. 'ductorscf transmissionlines H and 12 are connected directly to the inner conductors of trans-.mission lines .83 and 64, which lines correspond exactly to thetransmission lines .63 and 64 of Fig. 5, the impedance of lines 63 and64 being 50 ohms at the point or" connection. The outer conductors oflines 63 and .64 are connected to corresponding edges 19 and 39 of thecentrally located slots. mitter the .transmission .line assembly isidentical to that shown in Fig. 5. The remaining slots being connectedin like manner, each stack of slots is fed in the same phase toproduoean over- .all circular radiation pattern in the horizontal plane andcompressed in the vertical direction.

The previously described underlying principles of the invention can beapplied .inmany ways to utilize a number of useful antenna systems. Forexample, a highly improved omni-directional .radio range antenna ofextremely simple and convenient construction may be obtained byemploying a multiple slotted structure as shown at 24 in Figure 2 andapplying R. F. excitation according to the invention to derive the sameR. F. field patterns presently developed by means of a relativelycomplexantenna system.

The prior art omni-directional radio range, or omni-range as it istermed by the artisan, requires five antennas, four being arranged todefine a square with a fifth antenna being located at the geometricalcenter thereof. For vertical polarizationof the fields, dipoles areused, and loop antennas are used to provide horizontal polarization,

the central loop sometimes being arranged above From this point on tothe trans- The inner con- 7 the .others because of space limitations butthe arrangement remains essentially the same in principle. In eitherevent thecentral antenna is excited with .R. energy .at carrier wavefrequency to provide .a reference voltage and the othervantennas areexcited by suppressed-carrier .side band waves to produce a rotating R.,F. field.

The central antenna is pulsed to radiate a carrier frequency waveat someorienting direction, usuallynorth in actualpractice, so that the phaseanglebetween the reference field and the rotating .fieldis proportionalto the azimuthal angle from the orienting direction.

This is accomplished by means of an antenna according to the .inventionwherein the arrangement of Fig. 4 is employed to radiate a rotatingmagnetic field-the phase angle of which is utilized to determine thedirection of an observer with respect to the antenna. This is shown inFig, 17 whereinone pair of side-bands are applied at A and the remainingside-bands are applied at B, it being recognized that the feedarrangement .is thesame as that for Fig. 4 but drawn in an invertedposition. Components producing the carrier .andside bands are not shownnor will they be described in detail since they are quite well .known inthe art. It the-diameter of cylinder 24 does not exceed 0.4 wavelengthat the operating frequency the pattern resulting from the side bands fedat A can beexpressed as proportional to=cos 0 and that produced by sidebands applied at B will be proportional to sin 0. Preferably the lengthL is made one quarter wavelength or .an

odd multiple of quarter wavelengths long at the operating frequencysolely to obtain desirable impedance matching, but it should beunderstood that this length plays no part in preventing coupling betweenthe feed systems.

By means of a transmission .line assembly comprising a coaxialtransmission line which is bifurcated to form lines 8| and 82 of equallength which are in turn bifurcated to form equal length lines 83-86whereby the carrier wave applied to line '80 at C is applied in the samephase to all slots of element 24, the inner conductors of lines '83,.84,and 86 are connected to corresponding edges 48, 46, 42 and 44respectively, the outer conductors being connected respectively 'to therespective opposite edges 49, 41, 43 and 45 as shown. There will be nointeraction between'the feed system since the voltage applied at A willnot induce any potential across the north or south slots and hence nosignal from A will be transmitted along lines 83 and 84 and potentialsat the far ends of lines 85 and 86 will be out of phase so that nosignal from A will be transmitted along line 82. By similar analysis itcan be seen that there will be no interaction between signals applied atA, B and C. Applying one set of side bands at A, one set at B, and thecarrier at C in the manner heretofore employed in omniranges will resultin the transmission of two radio waves having a phase differenceproportional to the azimuthal angle from a given reference angle atwhich the carrier is impressed.

For practical considerations, it has been .found preferable inomni-range applcations to employ a slot length between one half and awavelength long with a radiatordiameterof 0.3 wavelength although it isto be understood that these dimensions are neitherabsolute nor critical.

The fact that the slot length is not too critical for .operation attolerable efliciencies provides a means-for adding to the versatility ofthe novel antenna system previously described. It is .con-

templated that in actual practice it will be highly desirable for aradio broadcasting station to provide both FM and television services tothe community in which it is located. For economical. and aestheticalreasons a single antenna system such as that shown in Fig. 8 will provehighly advantageous. Here the antenna is excited by a television signalapplied near the centers of the slots as previously described withreference to Fig. 4 and further excited at points a bit remote from thecenters of the slots by an FM signal of frequency different from that ofthe television signal. For example, a television signal at 67.25 mc./s.can be applied across the slots of length especially favorable to thatservice and an FM signal at 97.3 mc./s. applied across the slots at apoint approximately one half the distance between the centers and theends of the slots; the slots being excited substantially as full waveelements for the lower frequency and substantially as one and one-halfwave elements for the higher frequency. Obviously the relationship ofthe frequencies can be inverted while retaining the principle ofoperation whereby little or no interaction between the signals will takeplace.

Further interaction is also prevented, especially when there is noharmonic relationship at all between the signal frequencies, by makingthe feeder assembly for one frequency a quarter wavelength at the otherfrequency and vice versa as shown in Fig. 8. The exact points ofexcitation are not critical, however, and moreover a means of providinga desirable impedance match is constituted by moving the points ofexcitation along the slots.

By use of the arrangement of Fig. 5, or that of Fig. 6, a plurality ofelements may be stacked in the vertical direction if desired. Inasmuchas it is expected that the antenna systems described will lendthemselves to any and all R. F. installations, it is also contemplatedthat the interior of the conductive element be protected from theelements by covering the slots with some form of insulating materialhaving a low loss factor and preferably being transparent to provide ameans whereby a visual inspection may be made of the interior withoutremoving access covers and so forth. One such material suggested iswidely known as Plexiglas, and polyethylene has also been used withexcellent results.

While the invention has been described with reference to several expressembodiments thereof, it is understood that many obvious modificationswill be suggested to those skilled in the art without departing from thespirit and the scopeof the invention.

I claim:

1. An antenna system comprising a radiator element of hollow cylindricalconductive tubing having four longitudinally arranged slots therein andequally spaced about the periphery thereof, a first length oftransmission line having one conductor connecting the edges ofdiametrically opposed slots lying on the same side of a plane passingdiametrically through said cylindrical tubing and between thelongitudinal edges of said slots and having the other conductorconnecting the remaining edges of said slots, a second length oftransmission line connecting the edges of the other diametricallyopposed slots lying on the same sides of a plane passing diametricallythrough said cylindrical tubing and between the longitudinal edges ofsaid other slots, and means to apply radio frequency energy in phasequadrature to the midpoints of said first and second I6 lengths oftransmission line thereby to produce a rotating radio frequency fieldabout said radiator element.

2. An antenna system comprising a radiator element of hollow cylindricalconductive tubing having four longitudinally arranged slots therein,said slots being organized about a common longitudinal axis of saidelement to effect pairs of slots in registry, a first length oftransmission line having one conductor thereof connecting the edges of apair of slots lying on the same side of a plane passing through saidcommon axis and between the edges of said slots and having the otherconductor thereof connecting the remaining edges of said slots, a secondlength of transmission line connecting the edges of the other slots inlike manner, said transmission lines being connected substantially atthe midpoints of said slots, and means to apply radio frequency energyin phase quadrature to the midpoints of said first and second lengths oftransmission line thereby to produce a rotating radio frequency fieldabout said radiator element.

3. An antenna system including a conductive surface element having atleast two elongated slots arranged in parallel relationship therein, theedges of said slots in a given direction transverse to the longitudinalaxis of said slots being designated A, B, C, D in the order named, edgesA and B being opposing edges of one slot and edges 0 and D beingopposing edges of the other slot, means to apply radio frequency energyto said element, said means comprising radio frequency transmission linestructure applying instantaneous in-phase potentials of given polaritysimultaneously to edges B and. C and of polarity opposite to said givenpolarity simultaneously to edges A and D.

4. An antenna system including a tubular conductive member having atleast two elongated slots arranged in parallel relationship therein, theedges of said slots in a given direction about the periphery of saidmember being designated A, B, C, D in the order named, edges A and Bbeing opposing edges of one slot and edges C and D being opposing edgesof the other slot, means to apply radio frequency energy to said member,said means comprising radio frequency transmission line structureapplying instantaneous inphase potentials of given polaritysimultaneously to edges B and C and of polarity opposite to said givenpolarity simultaneously to edges A and D.

5. An antenna system including a tubular conductive member having atleast a pair of slots therein spaced about the periphery thereof, withthe edges of said slots defining parallel planes passing centrallythrough said member, means to apply radio frequency energy to saidmember, said means including equal lengths of transmission lineconnected in parallel at the ends thereof, said lengths of transmissionline being connected at the other ends thereof individually to saidconductive member at the edges of said slots, conductors of said lengthsof transmission line having ends connected together being connectedindividually at the opposite ends to the edges of said slots which arein the same one of said planes, thereby to produce a capacitivereactance component at the point of connection of said conductive memberto said lengths of transmission line.

6. An antenna system including a tubular conductive member having atleast a pair of slots therein spaced about the periphery thereof, withthe edges of said slots defining substantially parallel planes passingthrough, said member, means to apply radio-frequency energy to saidmember, said means including equal lengths of transmission lineconnected in parallel at the ends thereof, said lengths of transmissionline being connected at the other ends thereof individually to saidconductive member at the edges of said slots, conductors of said lengthsof transmission line having ends connected together being connectedindividually at the opposite ends to the edges of said slots which arein the same one of said planes.

'7. Anantenna system including a tubular conductive member having atleast a pair of slots therein spaced about the periphery thereof, withthe edges of. said slots defining substantially parallel planes passingthroughsaid member, means to, apply radio-frequency energy to saidmember, said means including, a lengthof coaxialtrans mission linehavingcenter and sheath, conductors, the endsof said conductors beingconnected at the opposite ends thereof to theuedgesof said slots whichare in. the same one of; said planes, and meansto couple utilizationapparatus at the midpoint of said. length of coaxial transmission line.

8; An antenna system, including a conductive surface element havingatleast four elongated slots arranged in. parallel, relationshiptherein, the edges of said slotsina given direction, transverse tothelongitudinal axis of the slots being designated 'A, a, B, b, C; c, D, din the order named, edges A and a being apposing edges of one slot andedges B and I) being apposing edges ofv another slot, means to applyradio-frequency energy tosaid element, said means. comprisingradio-frequency transmission. line structure applying instantaneousin-phase potentials ofgiven polarity. simultaneously to edges A and. cand. of. polarity. opposite to said given polarity simultaneously. toedges a and C, whereby substantial zero potential exists across edgesBand D and across edges D; and cl.

9. An antenna system including a conductive tubular member having aplurality of pairs of complementary slots arrangedabout the peripherythereof in substantially. parallel relationship therein, the edges of.the complementary slots defining non-intersecting substantially. planesurfaces passing through said member, means to apply radio-f-requencyenergy across eachof said slots to render the edges of complementaryslots lying in one of said planes of: oneinstantaneous polarity and theedges of said complementary slots lying in the other of said. planes. ofin,- stantaneous polarity-opposite to saidone polarity wherebyinstantaneous currents induced by complementary slotsfiow inopposingdirections about the periphery of said. conductive tubular.member.

10. An antenna system including a. tubular conductive radiator structurehaving an. even number of slots arranged longitudinally, therein, slotslocated substantially on opposite sides of said structure complementingeach other, the longitudinal edges of, said complementary slots definingsubstantially parallel plane surfaces passing through said structure,and means to apply radio-frequency wave energy across said complementaryslots, both of the edges of each pair of complementary slots lying inthe same one of said plane surfaces-being energized in the same phaserelationship.

11. An antenna system including a, radiator section comprising a hollowcylindrical member having four elongated slots substantiallylongitudinall arranged and equally spaced about the periphery thereof,opposing ones of said slots being coupled in pairs, the longitudinaledges of each of said pairs of slots defining a pair of substantiallyparallel plane surfaces passing through said member, means to applyradio-frequency energy in the same phase to each of said slots in eachof said coupled pairs of slots with the edges of said pairs of slotslying in the same one of said surfaces having the same instantaneouspolarity, and means to apply radio frequency energy to said coupledpairs of slots in phase quadrature to radiate a radio frequency wavehaving a circular horizontal pattern.

12. An antenna system including a stack of radiator sections eachcomprising a hollow cylindrical member having four elongated slotssubstantially longitudinally arranged and equally spaced about theperiphery thereof, opposingones of said slots being coupled in pairs,the longitudinal edges of each of said pairs of slots defining a pair ofsubstantially parallel plane surfaces passing through said member, meansto apply radio-frequency energy in the same phase to each of said slotsin each of said coupled pairs of slots of each stack of slots with theedges of said pairs of slots lying in the same one of said surfaceshaving the same instantaneous polarity, and means to applyradio-frequency energy to said coupled pairs of stacked slots in phasequadrature to radiate a radio-frequency wave having a circularhorizontal pattern and a directive vertical pattern.

13. An antenna system including a hollow conductive tubular memberhaving at least two slots arranged therein, opposing edges of said slotsdefining a pair of substantially parallel plane surfaces passing throughsaid member, means to apply radio frequency energy across the apposingedges of one of said slots, and means. interconnecting the opposingedges of said slots to apply said radio frequency energy to the other ofsaid slots with the edges of said slots lying in the same one of saiddefined planes being excited in the same instantaneous polarity.

14. An antenna system comprising a tubular conductive supporting memberhaving two complementary pairs of elongated slots arrangedlongitudinally therein, the slotsof each of said pairs being insubstantially exact alignment across the interior of said tubularsupporting member, each pair of said slots being coupled by radiofrequency transmission lines. to apply radio frequency energy theretowith a longitudinal edge of one slot of each pair of slots at the sameinstantaneous polarity as the opposing longitudinal edge of theotherslot of said pair of slots, thereby to cause instantaneous radiofrequency currents to, flow in opposing directions about the peripheryof said member, means to apply radio frequency energy to radiofrequency, transmission lines coupling one pair of slots, means to applyadditional radio frequency energy in phase quadrature to the firstnamed, energy to radio frequency, transmission lines coupling the otherpair of slots to produce rotating vector radiation of uniform intensityin the plane transverse to the longitudinal axis of said member meanS toapply further radio. frequency energy to radio frequency transmissionlines. coupling both, of said pairs of slotstoproduce a pulse, ofradiated energy of uniform intensity. in saidv plane, whereby. thedirection of radiation with respect to said member is proportional tothe phase angle between said rotating vector radiation and. said pulsedradiation with respect to the angle of said rotating vector radiation atwhich said pulse is emitted.

15. An antenna system comprising a tubular conductive supporting memberhaving two complementary pairs of elongated slots arrangedlongitudinally therein, the slots of each of said pairs being insubstantially exact alignment across the interior of said tubularsupporting member, each pair of said slots being coupled by radiofrequency transmission lines to apply radio frequency energy theretowith a longitudinal edge of one slot of each pair of slots at the sameinstantaneous polarity as the opposing longitudinal edge of the otherslot of said pair of slots, thereby to cause instantaneous radiofrequency currents to flow in opposing directions about the periphery ofsaid member, means to apply radio frequency energy corresponding to afirst pair of sidebands of a modulated radio frequency carrier wave toradio frequency transmission lines coupling one pair of slots, means toapply additional radio frequency energy corresponding to a second pairof sidebands of said modulated carrier wave to radio frequencytransmission lines coupling the other pair of slots, and means to applyradio frequency energy corresponding to said carrier wave to radiofrequency transmission lines coupling both of said pairs of slots.

16. An antenna system comprising a tubular conductive member having atleast a pair of elongated slots arranged in the walls thereof, themidpoints of the corresponding edges of said slots being substantiallydiametrically opposed, and means to couple a source of radio frequencyenergy across the edges of both slots of said pair of slots, one edge ofone of the slots of said pair and the edge of the other slot opposingthe one edge of said one slot being excited in the same instantaneouspolarity and phase, and the remaining edges of the slots beingsimultaneously excited in the opposite instantaneous polarity and phase.

17. An antenna system comprising a tubular conductive member having atleast a pair of elongated slots arranged in the walls thereof, themidpoints of the corresponding edges of said slots being substantiallydiametrically opposed, and

means to couple the conductors of a transmission line across the edgesof both slots of said pair of slots, one conductor of said transmissionline being coupled to one edge of one of the slots of said pair, anotherconductor of said transmission line being coupled to the other edge ofsaid one slot and to the edge of the other slot corresponding to the oneedge of said one slot, and the remaining edge of the other slot beingcoupled to said one conductor of said transmission line.

18. An antenna system comprising a hollow conductive member having atleast a pair of elongated slots arranged in the walls thereof with thelongitudinal edges thereof substantially parallel to each other and thelongitudinal axis of said hollow conductive member, the correspondingedges of said slots appearing in the same relative position in atraverse about the periphery of said member in a single direction, meansto apply radio frequency energy across apposing edges of said slots, andmeans to couple the non-corresponding edges of both slots of said pairof slots together.

19. An antenna system comprising a tubular conductive member having atleast a pair of elongated slots arranged in the walls thereof with thelongitudinal axes thereof substantially parallel to each other and thelongitudinal axis of said tubular conductive member, the correspondingedges of said slots being substantially diametrically opposed, and meansto couple the conductors of a transmission line across the edges of bothslots of said pair of slots, one conductor of said transmission linebeing coupled to one edge of one of the slots of said pair, anotherconduetor of said transmission line being coupled to the other edge ofsaid one slot and to the edge of the other slot corresponding to the oneedge of said one slot, and the remaining edge of the other slot beingcoupled to said one conductor of said transmission line.

20. An antenna system comprising a tubular conductive member having atleast a pair of elongated slots arranged in the walls therewith with thelongitudinal axes thereof substantiall parallel to the longitudinal axisof said tubular conductive member, the corresponding edges of said slotsbeing substantially diametrically opposed, means to apply radiofrequency energy across apposing edges of both slots of said pair ofslots, a first conductor connecting one edge of one of the slots withthe opposing edge of the other slot of said pair, a second conductorconnecting the other edge of said one slot to the other edge of theother slot.

21. An antenna system comprising a tubular conductive member having atleast a pair of elongated slots arranged in the walls therewith with thelongitudinal axes thereof substantially parallel to the longitudinalaxis of said tubular conductive member, the corresponding edges of saidslots being substantially diametrically opposed, and means to couple theconductors of a transmission line across the edges of both slots of saidpair of slots, one conductor of said transmission line being coupled toone edge of one of the slots of said pair, another conductor of saidtransmission line being coupled to the other edge of said one slot andto the edge of the other slot corresponding to the one edge of said oneslot, and the remaining edge of the other slot being coupled to said oneconductor of said transmission line,

22. An antenna system comprising a tubular conductor having two pairs ofelongated slots arranged therein longitudinally of the axis of saidtubular conductor, the corresponding edges of each pair of slots beingdiametrically opposite, means to apply radio frequency energy acrossapposing edges of each of the slots of one of said pairs of slots withopposing edges of the slots of each of said pair being excited the sameinstantaneous polarity thereby to cause instantaneous radio frequencycurrents to flow in opposing directions about said conductor and toproduce substantially zero potential corresponding to said radiofrequency energy across the remaining slots, and means to applyadditional radio frequency energy across apposing edges of the otherpair of slots in the same polarity and phase relationship as in said onepair of slots thereby to cause instantaneous radio frequency currentscorresponding to said additional radio frequency energy to flow inopposing directions about the periphery of said conductor and to producesubstantially zero potential across the first of said slots.

23. An antenna system comprising a tubular conductor having two pairs ofelongated slots arranged therein longitudinally of the axis of saidtubular conductor, the corresponding edges 15 ofv eachpair of slots;being substantiallydiametrrically opposed;.means to apply radiofrequencyenergy across two apposing edges. of slots with opposing edges of saidtwo slots excited in. the.

same instantaneous polarity thereby to cause instantaneous radiofrequency currents; to: fiowin opposing directions about saidconductorand.

to produce substantially zero potential corresponding to said radiofrequency-energy across. theremaining slots, and" means to apply addi.tionalradio. frequency energy in phase quadrature with said firstnamedenergy acrossapposing edges of the other pair of. slots in the:same. polarity and phase. relationship as: in: the-first. named slotsthereby to cause. instantaneous radio frequency currents. corresponding;to said additional radio frequency energy to flow in opposing directionsabout the. periphery of, said conductor and to produce substantiallyzero potential across the first of said slots, wherebysaid instantaneousradio frequency currents are combined to produce omni-directionalradiation aboutsaid conductor;

24'. An. antenna. system comprising a tubularconductor having two pairsofslots arranged therein longitudinally of'the longitudinal axis of saidconductor, the corresponding edges of each pair of slotsbeingsubstantially diametrically opposed, means to apply radio frequencyenergy across apposing edges ofone pair of slots, opposing edges of saidone pair of slots being excited in the same instantaneous polarity,thereby to cause instantaneousradi'o frequency currents to flow inopposing directions about said conductors and to produce substantiallyZero; potential corresponding to saidzradio. frequency energy acrosstheremaining slots, means to apply additional radio frequency energy inphase quadrature to said first named energy across apposing edges of theother pair of slots in the same instantaneous polarity and phaserelationship as. for said one pair of slots thereby to causeinstantaneous radio frequency currents corresponding to said additionalradio frequency energy to flow in opposing direotions about theperiphery ofsaid con.- ductor and to produce substantially zeropotential across the first named slots to produce. rotating vectorradiation of uniform intensity in. the plane normal to the longitudinal.axis. of said conductor.

25. An antenna system comprisin a tubular conductive member. having aplurality of 'pairs of i6 longitudinal complementary slots. arrangedabout the: periphery thereof, opposing edges. of each pair ofcomplementary slots defining. a pair of non-intersecting planes passingthrough said member, the planes-of one pair of complementary slotsintersecting similar planesv of other pairsof complementary slots withinsaid member, andmeansto apply the. same radio-frequen-- cy energy acrossboth complementary slotsof said one pair. with the edges. comprisingthenonintersecting planes? excited in the same instantaneous'polaritythereby tdproduce substantially zero. potential difference acrossapposingedges. of the, remaining pairs of slots due tocurrents. inducedaround said member by said. applicationof radio frequency energy; tosaid one pair of slots.

26..An antenna. system= comprising a conductive tubular member: having aplurality of pairs of longitudinal slots arranged about the peripherythereof, the slots of eachpair being located on substantiallyoppositesides. of said member, means to apply radio frequency energyacross. apposing edges of one slot. of: one pair of slots. to induceinstantaneous currents in one direction about the periphery of saidmember, and means to apply the'same radio frequency energy across.apposing, edges of the'other slot. of said onepair of slots withopposite instantaneous polarity about the periphery" thereby to induceinstantaneous currents in. the opposite: directionabout the. peripheryof said-member.-

GEORGELH. BROWN.

References Gited in the file. of. this patent UNITED STATES PATENTSOTHER- REFERENCES.

Electronics, Jordan and Miller; February 1947-, pages 9'0'to 93;

Radio, July 1946; pages-14 and 15.

F. M. & Television, September 1946; pages45 to Electronics; September1948'; pages 103- to 107.

